In a number of applications, it may be necessary to deliver precise amounts of gases or other fluids to processing chambers and/or other processing facilities. These applications may include, but are not limited to, the fabrication of semiconductor systems.
For some applications, it may be necessary to divide or split combined process gases or other fluids among multiple processing facilities. Examples of flow splitting applications may include, but are not limited to, etching, stripping, and PECVD (Plasma Enhanced Chemical Vapor Deposition). In these cases, a single outlet of a gas box that contains the combined process gases may be connected to multiple chambers and/or processing facilities, through secondary flow channels.
An FRC (flow ratio controller) may be used to divide a primary flow among a plurality of secondary flow channels, in accordance with preselected ratios. A number of designs have been implemented for dual channel flow ratio controllers (DCFRCs), which split a single mass flow into two secondary flow channels.
In some applications, a multiple-channel flow ratio controller (MCRFC) may be needed in order to split a single mass flow into more than two secondary flows. In one approach, an MCFRC may be implemented by linking a number of DCFRCs in a cascaded configuration. The cascaded configuration may result in a high pressure drop across the MCFRC, however. Also, the cascaded set of DCFRCs may have a large footprint, and be costly. Further, the cascaded configuration for DCFRCs may constrain the total number N of flow channels to be N=2n, which may considerably decrease flexibility.
Accordingly, there is a need for improved systems and methods for implementing an MCFRC.